The patch titled
Subject: set_task_comm: kill the pointless memset() + wmb()
has been added to the -mm tree. Its filename is
set_task_comm-kill-the-pointless-memset-wmb.patch
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------------------------------------------------------
From: Oleg Nesterov <oleg@xxxxxxxxxx>
Subject: set_task_comm: kill the pointless memset() + wmb()
set_task_comm() does memset() + wmb() before strlcpy(). This buys nothing
and to add to the confusion, the comment is wrong.
- We do not need memset() to be "safe from non-terminating string
reads", the final char is always zero and we never change it.
- wmb() is paired with nothing, it cannot prevent from printing
the mixture of the old/new data unless the reader takes the lock.
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Andi Kleen <andi@xxxxxxxxxxxxxx>
Cc: John Stultz <johnstul@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/exec.c | 10 ----------
1 file changed, 10 deletions(-)
diff -puN fs/exec.c~set_task_comm-kill-the-pointless-memset-wmb fs/exec.c
--- a/fs/exec.c~set_task_comm-kill-the-pointless-memset-wmb
+++ a/fs/exec.c
@@ -1027,17 +1027,7 @@ EXPORT_SYMBOL_GPL(get_task_comm);
void set_task_comm(struct task_struct *tsk, char *buf)
{
task_lock(tsk);
-
trace_task_rename(tsk, buf);
-
- /*
- * Threads may access current->comm without holding
- * the task lock, so write the string carefully.
- * Readers without a lock may see incomplete new
- * names but are safe from non-terminating string reads.
- */
- memset(tsk->comm, 0, TASK_COMM_LEN);
- wmb();
strlcpy(tsk->comm, buf, sizeof(tsk->comm));
task_unlock(tsk);
perf_event_comm(tsk);
_
Patches currently in -mm which might be from oleg@xxxxxxxxxx are
poweroff-change-orderly_poweroff-to-use-schedule_work.patch
thinkpad-acpi-kill-hotkey_thread_mutex.patch
kthread-introduce-to_live_kthread.patch
kthread-kill-task_get_live_kthread.patch
posix_cpu_timer-consolidate-expiry-time-type.patch
posix_cpu_timers-consolidate-timer-list-cleanups.patch
posix_cpu_timers-consolidate-expired-timers-check.patch
lockdep-introduce-lock_acquire_exclusive-shared-helper-macros.patch
lglock-update-lockdep-annotations-to-report-recursive-local-locks.patch
teach-argv_split-to-handle-the-mutable-strings.patch
epoll-use-rcu-to-protect-wakeup_source-in-epitem.patch
ptrace-add-ability-to-retrieve-signals-without-removing-from-a-queue-v4.patch
selftest-add-a-test-case-for-ptrace_peeksiginfo.patch
usermodehelper-export-_exec-and-_setup-functions.patch
usermodehelper-export-_exec-and-_setup-functions-fix.patch
kmod-split-call-to-call_usermodehelper_fns.patch
keys-split-call-to-call_usermodehelper_fns.patch
coredump-remove-trailling-whitespaces.patch
split-remaining-calls-to-call_usermodehelper_fns.patch
kmod-remove-call_usermodehelper_fns.patch
coredump-only-sigkill-should-interrupt-the-coredumping-task.patch
coredump-ensure-that-sigkill-always-kills-the-dumping-thread.patch
coredump-sanitize-the-setting-of-signal-group_exit_code.patch
coredump-introduce-dump_interrupted.patch
coredump-factor-out-the-setting-of-pf_dumpcore.patch
coredump-change-wait_for_dump_helpers-to-use-wait_event_interruptible.patch
set_task_comm-kill-the-pointless-memset-wmb.patch
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